The present invention relates to a vehicle headlamp unit with a light source of a discharge lamp, and to a vehicle headlight with the headlamp unit.
A conventional headlight for a motor vehicle typically used was a projector type headlight or a multi-reflector type headlight with a light source of a halogen light bulb (iodine light bulb), a lens and a precisely condensing reflector arranged around the halogen bulb.
The projector type headlight adopts a standardized PE (poly-ellipsoid) reflector or DE (three dimensional ellipsoid) reflector, and the multi-reflector type headlight adopts a MS (multi-surface) reflector.
The halogen light bulb used for the headlight is nearly a point source of light with a relatively high efficiency of about 20 lumens/watt and a consumption power of 35-60 watts. Such halogen bulb operates at a low power voltage of 12 or 24 volts and therefore no specific electrical insulation is required. An average lifetime of the halogen bulb is about 400 hours. Due to the difference of bulb shapes, there are a plurality of specifications in the halogen bulb such as H-1 type, HB-1 type, H-4 type, HB-4 type, HB-5 type and H-7 type. For each type, a shape and a dimension of a light-bulb base made of plastic or ceramic are standardized.
In the past, the switching between high beam mode and low beam mode in the halogen bulb vehicle headlight had been performed by selectively turning-on one of two halogen bulbs respectively disposed at centers of the high beam reflector and the low beam reflector. Recently, such switching is performed by selectively turning-on one of two filaments in a single halogen light bulb, which are disposed with a distance of several millimeters each other. Namely, high beam light distribution is obtained by tuning-on only the high beam filament and by reflecting light from the filament at a reflector, whereas low beam light distribution is obtained by tuning-on only the low beam filament and by reflecting light from the filament at the same reflector in different condensing manner. The halogen bulbs of H-4 type, HB-1 type and HB-5 type are such two filaments bulbs.
FIGS. 1a and 1b show a cross sectional view and a side view of a HB-1 type halogen bulb with two filaments for high beam and low beam, and FIG. 2 shows a side view of the halogen bulb fitted in a socket that is fixed to a base.
As shown in these figures, the HB-1 type halogen bulb 10 has a high beam filament 12 and a low beam filament 13 in a glass capsule 11. The high beam filament 12 and the low beam filament 13 are located at different positions each other along a direction substantially perpendicular to the light axis Z of the halogen bulb. The halogen bulb 10 is fitted in the specific socket 14 that is fixed to the specific base 15. A black lightproof coating 16 is applied to the top end section of the glass capsule 11 to provide no glare from the filaments. Three terminal electrodes (including common grand electrode) 17 for the two filaments are formed in the rear of the base 15 as shown in FIG. 2. These electrodes 17 are electrically connected to a lighting circuit through lead lines, connectors and ground (not shown).
FIGS. 3a and 3b show a cross sectional view and a side view of a HB-5 type halogen bulb with two filaments for high beam and low beam.
As shown in these figures, the HB-5 type halogen bulb 30 also has a high beam filament 32 and a low beam filament 33 in a glass capsule 31. The high beam filament 32 and the low beam filament 33 are located at different positions each other along a direction substantially perpendicular to the light axis Z as well as in HB-1 type halogen bulb. A black lightproof coating 36 is applied to the top end section of the glass capsule 31 to provide no glare form the filaments.
The high beam filament 12 and the low beam filament 13 of the above-mentioned halogen bulb 10 are spaced by several millimeters from each other along a direction substantially perpendicular to the light axis Z as well as the high beam filament 32 and the low beam filament 33 of the halogen bulb 30. The filaments 12 and 13 of the HB-1 type halogen bulb 10 run along a direction perpendicular to the light axis Z whereas the filaments 32 and 33 of the HB-5 type halogen bulb 30 run along a direction parallel to the light axis Z. The length of these filaments 12, 13, 32 and 33 is about 5 millimeters.
Recently, the adoption of a headlamp unit with a high intensity discharge (HID) lamp is studied and put partially to practical use as a next-generation vehicle headlight instead of the vehicle headlight using the halogen bulb(s).
The discharge lamp used in such vehicle headlamp unit operates with a high power voltage of about 20,000 volts, and radiates light with a extremely high efficiency of about 100 lumensxc2x115%/watt for example. Thus, the discharge lamp provides light flux substantially twice as strong as that of the halogen bulb and low power consumption, typically about 35 watts. Further, the discharge lamp has a lifetime of about four times as long as that of the halogen bulb. Therefore, the discharge lamp saves energy and thus is extremely ideal for a vehicle headlight.
However, a conventional vehicle headlamp unit using such discharge lamp has following disadvantages:
(1) It is impossible to form two light sources in a single bulb like as H4 type, HB-1 type and HB-5 type halogen bulbs;
(2) Mounting of two individual discharge lamps near the center of a reflector is difficult due to no enough space and causes the design of the reflector to make difficult and the manufacturing cost of the reflector to increase; and
(3) Glare cannot be prevented if a discharge lamp is substituted for a halogen bulb in the vehicle headlamp unit.
The applicant of this application has proposed, in U.S. Pat. Ser. No. 09/562,863, a vehicle headlamp unit with a discharge lamp, a shade arranged near the discharge lamp and a moving means for relatively moving the discharge lamp and the shade relative to each other by sliding one of them in a direction along the light axis of the headlamp unit or by rotating one of them so as to switch between high beam mode and low beam mode.
However, this proposed headlamp unit cannot be compatible with a headlamp unit with a halogen bulb having a high beam filament and a low beam filament located at different positions each other along a direction substantially perpendicular to the light axis Z, such as an HB-5 type halogen bulb or an HB-1 type halogen bulb. Namely, in case of the proposed headlamp unit relatively moving the discharge lamp and the shade by sliding one of them in a direction along the light axis, positions of the light source will differ from the filament positions of the HB-5 type or HB-1 type halogen bulb as a matter of course. In case of the proposed headlamp unit for relatively moving the discharge lamp and the shade by rotating one of them, the light axis direction will change causing its light distribution to differ from that of the headlamp unit with the HB-5 type or HB-1 type halogen bulb.
For the halogen bulb used for vehicle headlight, a black lightproof coating is in general applied to its top end section so as to shield light along the light axis Z and thus to prevent glare from the filaments, as shown in FIGS. 1b, 2 and 3b. However, in case of the discharge lamp, it is impossible to apply such black lightproof coating to its top end section due to its shape and size.
It is therefore an object of the present invention to provide a vehicle headlamp unit with a discharge lamp and a vehicle headlight with the headlamp unit, whereby it is compatible with a headlamp unit with a halogen bulb that has a high beam filament and a low beam filament located at different positions each other along a direction substantially perpendicular to the light axis, and can provide correct light distributions of high beam mode and low beam mode as well as the halogen bulb head lamp unit.
Another object of the present invention is to provide a vehicle headlamp unit with a discharge lamp and a vehicle headlight with the headlamp unit, whereby prevention of glare can be easily attained.
According to the present invention, a vehicle headlamp unit includes a discharge lamp, a socket to which the discharge lamp is fitted, a base carrying the socket and being compatible with a base of a halogen bulb provided with a high beam filament and a low beam filament, and a moving mechanism, in response to a high beam mode or a low beam mode, for moving the socket in parallel along a direction perpendicular to a light axis of the vehicle headlamp unit without inclining a light axis of the discharge lamp.
Also, according to the present invention, a vehicle headlight has a reflector, a lens arranged in front of the reflector and a vehicle headlamp unit with a light-emitting portion arranged in front of the reflector. The vehicle headlamp unit includes a discharge lamp, a socket to which the discharge lamp is fitted, a base carrying the socket and being compatible with a base of a halogen bulb provided with a high beam filament and a low beam filament, and a moving mechanism, in response to a high beam mode or a low beam mode, for moving the socket in parallel along a direction perpendicular to a light axis of the vehicle headlamp unit without inclining a light axis of the discharge lamp.
Since the base is compatible with a base of a halogen bulb provided with a high beam filament and a low beam filament and the socket and the discharge lamp fitted to the socket is movable in parallel along a direction perpendicular to a light axis of the vehicle headlamp unit without inclining a light axis of the discharge lamp in response to a high beam mode or a low beam mode, this headlamp unit can be adopted as it is to any vehicle headlight using a light source of a halogen bulb instead of the halogen bulb headlamp unit. Also, it is possible to provide correct light distributions of the high beam mode and the low beam mode as well as the halogen bulb headlamp unit.
Furthermore, since the discharge lamp moves in parallel along a direction perpendicular to the light axis of the headlamp unit without inclining the light axis of the discharge lamp, light distribution of from the discharge lamp will not change due to the movement. Thus, perfectly the same high beam and low beam light-distributions as the halogen bulb headlamp unit can be expected.
It is preferred that the moving mechanism linearly moves an light-emitting portion of the discharge lamp between positions corresponding to a position of the high beam filament and a position of the low beam filament.
It is also preferred that the vehicle headlamp unit further includes a cylindrical housing being integral with the base, and that the moving mechanism is mounted in the housing. Since the moving mechanism is accommodated in the housing to attain a smaller size of the headlamp unit, interchange of this headlamp unit to the conventional headlamp unit with a halogen bulb can be performed easily.
It is further preferred that the moving mechanism includes a first sliding member being slidable along a direction parallel to the light axis of the vehicle headlamp unit, a drive mechanism for driving the first sliding member in the direction parallel to the light axis of the vehicle headlamp unit, a second sliding member being integral with the socket and slidable along a direction perpendicular to the light axis of the vehicle headlamp unit, and a conversion mechanism for converting movement of the first sliding member along the direction parallel to the light axis of the vehicle headlamp unit to movement of the second sliding member along the direction perpendicular to the light axis of the vehicle headlamp unit.
It is preferred that the conversion mechanism includes at least one slit being formed in the second sliding member and running along a direction tilted with respect to the light axis of the headlamp unit in a plane including the directions parallel and perpendicular to the light axis of the headlamp unit, and at least one pins being attached to the first sliding member and slidable through the at least one slit.
It is also preferred that the conversion mechanism further includes at least one first sliding surface formed on the first sliding member and running along a direction tilted with respect to the light axis of the headlamp unit in a plane including the directions parallel and perpendicular to the light axis of the headlamp unit, and at least one second sliding surface formed on the second sliding member and running along a direction tilted with respect to the light axis of the headlamp unit in a plane including the directions parallel and perpendicular to the light axis of the headlamp unit, the at least one second sliding surface sliding over the at least one first sliding surface.
It is also preferred that the at least one first sliding surface and the at least one second sliding surface are located in front of the at least one slit and the at least one pin.
It is preferred that the drive mechanism is a solenoid located in a rear direction of the first sliding member.
It is preferred that the vehicle headlamp unit further includes a first shade fixed to the base for shielding a part of light radiated from the discharge lamp. In this case, it is more preferred that the vehicle headlamp unit further includes a second shade detachably attached to a top end section of the first shade for shielding a part of light forwardly radiated from the discharge lamp. Thus, no glare from the discharge lamp of the vehicle headlamp unit can be easily ensured.
It is further preferred that the base is a base being compatible with a base of an HB-5 type halogen bulb.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.